The development of EL devices each using a thin film formed of a luminous material has been advanced in recent years. In particular, research on, and the development of, an organic EL device have been vigorously advanced because of the potential of the device to serve as a light emitting device having high-speed responsiveness and high efficiency. In general, an organic EL device, that is, an organic light emitting device has such a structure that an anode and a cathode are formed as a pair of electrodes on a substrate, and plural organic compound layers including a light emitting layer are laminated between the pair of electrodes by employing, for example, a vapor deposition method.
A hole transporting layer and a hole injecting layer on an anode side with respect to the light emitting layer, and an electron transporting layer and an electron injecting layer on a cathode side with respect to the light emitting layer are appropriately provided as an organic compound layer.
In addition, at least one electrode of the anode and the cathode must be a light transmission electrode (transparent electrode) in order that light emitted from the light emitting layer may be extracted. An indium tin oxide (ITO), an indium zinc oxide (IZO), or the like is used in the transparent electrode.
When a display in which a large number of organic light emitting devices are arranged is driven by using an active matrix circuit, each organic light emitting device (pixel) must be connected with a pair of thin film transistors (TFTs) for controlling a current in the pixel.
In addition, an organic light emitting device deteriorates owing to moisture, so some contrivances to protect the organic light emitting device from external moisture or oxygen are needed. For example, the organic light emitting device must be covered with a sealing film, or must be affixed with sealing glass by using a resin, to seal the device hermetically, and an inert gas such as nitrogen must be sealed in the hermetically sealed area.
Here, a conventional active matrix type display apparatus will be described with reference to FIGS. 9 and 10.
A display pixel is established by laminating and forming a TFT and an organic light emitting device on a glass substrate 500. To be specific, a TFT 501 for driving the organic light emitting device is formed on the substrate 500. The TFT 501 is covered with an inorganic insulating layer 517, and is further covered with a planarizing layer 518 for planarizing the surface of the substrate. A reflecting electrode 520 is formed on the resultant.
The reflecting electrode 520 is patterned for each pixel, and the reflecting electrode 520 and the drain electrode of the TFT 501 are electrically connected to each other through a contact hole formed in each of the inorganic insulating layer 517 and the planarizing layer 518.
A device isolation film 530 is an insulating layer provided between adjacent pixels, and is placed so as to cover an edge portion of the reflecting electrode 520.
A hole transporting layer 523, a light emitting layer 522, and an electron transporting layer 524 are formed as an organic compound layer including a light emitting layer on the reflecting electrode (first electrode) 520 as an anode. Then, a transparent electrode (second electrode) 521 as a cathode is formed, whereby an organic light emitting device is completed (see FIG. 10).
A sealing substrate 540 is stuck to the substrate 500 by using an adhesive member 541 in order that the organic light emitting device having the above constitution may be protected from moisture.
The organic light emitting device deteriorates owing to the infiltration of not only moisture from the outside but also moisture taken in at the time of the formation of a TFT or of an electrode and present in an area surrounded by the substrate and a sealing film or sealing glass into the organic light emitting device. A source of moisture present in such area is, for example, the planarizing layer provided for planarizing the substrate and formed of an insulating resin such as a polyimide-based resin or an acrylic resin.
The planarizing layer not only discharges moisture but also serves as a path through which moisture infiltrating from the outside is propagated to infiltrate into the organic light emitting device. In view of the foregoing, attempts have been made to prevent the infiltration of moisture into the organic light emitting device by: separating the planarizing layer with a planarizing layer dividing portion provided outside a pixel area; and covering the separated portion with an electrode material to trap moisture in the planarizing layer (see Japanese Patent Application Laid-Open Nos. 2004-335267, 2005-164818 and 2006-58751).
In addition, when the organic compound layer of which the organic light emitting device is formed are formed in a continuous manner to straddle organic light emitting devices, not only the planarizing layer but also the organic compound layer itself serve as paths through which moisture infiltrating from the outside is propagated.
In a display apparatus having plural pixels, a nondisplay device (dummy pixel) is formed for securing the accuracy of a repeating pattern needed in an image forming step.
Nondisplay devices are each formed in the same manner as in a pixel in a display area, and are arrayed at the same interval as that of the pixels in the display area. However, the nondisplay devices are formed outside the display area, and are not actually driven.
In each of Japanese Patent Application Laid-Open Nos. 2004-335267, 2005-164818 and 2006-58751, a planarizing layer dividing portion is present at a boundary portion between the inside of a display area and the outside of the display area, or is present outside the display area so that the area of a peripheral part not used for display is increased. In addition, the area of a peripheral part is increased similarly in a nondisplay device.
Meanwhile, in a final product such as a mobile phone or a digital camera on which a display apparatus may be mounted, there has been a growing trend toward the implementation of pixels at a high density. Accordingly, in the display apparatus, a reduction in area of a peripheral part (frame) where no image is displayed in accordance with the size of the display apparatus has been requested. However, in a display apparatus of each of Japanese Patent Application Laid-Open Nos. 2004-335267, 2005-164818 and 2006-58751, the area of a peripheral part is increased, with the result that a frame area increases.